Diazotype layer containing three coupling components for neutral black shades



Patented Jan. 9, 1951 DIAZOTYPE LAYER CONTAINING THREE GOUPLING COMPONENTS FOR NEUTRAL BLACK SHADES Sam Charles Slifkin, Binghamton, N. Y., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application May 5, 1948, Serial No. 25,318

4 Claims.

This invention relates to diazotype light sensitive media. More particularly, it relates to that type of diazotype reproduction media wherein the reproductions obtained from exposure of the reproduction media under an original are developed in the dry state by contact with a gaseous developing agent. This application is a continuation-in-part of my copending application Serial Number 554,166, filed September 14, 1944, now abandoned.

Diazotypes of this class are produced by treating the surface of a suitable base such as paper, cellulose acetate film, cellophane, glass and metal surfaces with a solution of two dye components, one of which, the diazo compound, is the photo-sensitive body and the other azo component or coupling component is a compound capable of combining with the diazo compound to form an azo dye. The diazo compound will be decomposed upon exposure to'light, particularly light which emits rays in the 36005. to 4200A. line to form a compound which can no longer combine with the azo coupling component. Diazo compounds which are derived from p-diamines of the benzene series are most suitable for such, so-called, two component diazotypes.

When a diazotype layer containing a diazo compound and a coupling component is exposed under an original tracing, design or printed sheet to a proper source of light, the diazo compound, in those areas which are not protected by the solid lines of the tracing or design or letters of the printed sheet, is decomposed. Upon subsequent development, a dye forms only in the areas which were protected from thelight by the said lines of the tracing or design and the letters of the sheet, and thus, the original is reproduced in the color formed by the particular combination of diazo compound and coupling component present in the light sensitive layer. Dark colors and particularly blacks are most desired in technical reproduction'work for the reason that they are most permanent, produce the greatest degree of contrast, and reps resent a true reproduction ofblack line originals. Many formulae have been suggested purporting to yield a. truly .black line on a white background with varying degrees of success. For the most part, such formulae have been based upon the theory that the addition of two coupling components, one of which will produce a blue azo dye and theyother, a yellow azo dye with: the diam-compound, will. shade to;a :black.

2 With such a combination, it is very diflicult to achieve a. truly neutral black.

Now it has been discovered that the combina-'- tion of at least three selected coupling components will produce blacks which are uniformly neutral throughout the half-tones and full density areas. The selection of the coupling components for this process need not necessarily be based upon their ability to produce pure primary colors which have been found tobe extremely diflicult to form in diazotype dyes. It has rather been found highly desirable to use components forming colors which impart not only the basic hue desired but also shades of other colors which will balance to a neutral color. For example, if a coupler forming a blue is used with a coupler forming a yellow to produce a greenish black, then the addition of a-blue with a reddish cast will produce a neutral black. Furthermore, if the half-tones are neutral while the full tones are too green, then the formula may be rebalanced to permit addition of a bluish-red component having a slow coupling rate which will then exert its shading effect in full tones. If the reverse condition exists and half-tones are off balance, then a bluish-red component which is fast coupling and which, therefore, exerts its shading effect in the halftones, should be employed. The three or more coupling components should, therefore, be so selected that their combined 'efiect is to produce neutral shades in all density areas.

It has been observed that a given diazo com pound will couple at greatly varying rates with a series of different azo coupling components and a given coupling component will also couple at greatly varying rates with a series of diilerent diazo compounds. This coupling time relationship between diazo compounds and coupling components has been referred to as coupling potential. Thus one coupling component will have a higher coupling potential than another with respect to a given diazo compound.

So widely divergent are the coupling rates or coupling potentials of known couplers and diazo comp unds that a study of the kinetics of the coupling reactionindicates that there is a range of at least 1,000,000 to 1 in the relative coupling potentials. In view, of this great diiferential of coupling rates or coupling potential, the probabilities of finding couplers which will couple to produce complementary hues with the same diazo compound at identical coupling rates are very remote;

M In the production of diazotypes the: selection of such coupling components is of prime importance.

further confounded by the fact that not all coupling components can meet the fundamental requirements of good keeping qualities for both the sensitized reproduction material and the reproduced image, wash fastness, light fastness, resistance to yellowing due to aging and many other requirements of primary importance in diazotype formulation. Thus even if a coupler forming a complementary hue with another coupler at the same coupling rate could be found,

it may well be lacking in one or all of these prop erties essential to its use in diazotypes.

The concentration of the diazo compound available for coupling must also be considered.

While it may be possible to find a balance of i coupler concentrations between two couplers producing approximately complementary shades necessary to give the desired shade in one density, as for instance in the maximum or higher density area, the coupler balance will be tied to the d'iazo concentration in that density area. In those areas where the diazo concentration has beenreduced by exposure to light as in the half tones, balance is upset because of the unequal competition for the diazo set up between the couplers. The coupler of greater reactivity or higher coupling potential will prevail in this competition and hence the final shade in such areas will be predominantly that of the higher potential coupler. Hence it is not possible to automatically compensate for this variation when using only two cou lers of different coupling potentials. I have found that the addition of a third coupler having the necessary reactivity or coupling potential influences the shade only where the inadeouacy of the other two complementary couplers in the system demands. By the use of the pro er concentration of this additional coupler to limit its eiiect only to those density ranges where tonal correction is necessary, a measure of control is possible.

' The coupler or couplers added for improving the'kinetic balance of the coupling reactivity and compensating for the uneoualcompetition for the diazo compound should also compensate for color imbalance. If the two primary cou lers which produce approximately complementary shades balance to a dense near-black possessing too much of a red cast then a small amount of a coupler producing a greenish-blue shade is added. If the correction is required in the low density areas then a greenish blue coupler of high coupling potential is added or one of slow coupling potential if the required correction is in the high densities. In this way we may take advantage of primary cou ler cornbinations which produce colors of the highest tinctorial strength even though the shade produced by such combinations is not a neutral blaci: In following this technique of ba ancing the formula for producing neutral black reproduction, there may be used as many coupling com ponents as are necessary to achieve the ideal result, yet without the necessity of using coupling components of identical coupling potential. In the production of positive images by diatotypes the development due to coupling of the dye components is essentially instantaneous. Hence, the kinetics of the diazo and coupler system are Wherever photolysis has produced a diazo concentration difierent from that in the original formu a, the. altered. con

centration condition'produce a profound effect significance in" two component diazotype systems since the diazos used in such system are relatively slow-reacting. Hence the differential in the coupling potentials of the couplers is magnified as compared with that of the same couplers when used with faster reacting diazos. Only close observance of the foregoing relationships between coupling potentials, concentration, and shade balance permits the scientific formulation of the desirable uniform neutral black tones in all density areas.

According to this process, therefore, at least one coupling component is added to a diazotype combination containing a single diazo compound which will be derived from a p-diamine of the benzene series and two other coupling components which will react with that diazo compound to produce complementary shades, such as yellow and reddish-blue, which balance to produce near-black hues. The added coupler must have a compensating coupling potential for the coupler which will exert the least influence in the unbalanced density as explained above; it must be added in such concentration as to limit its effect to those density ranges where tonal correction is necessary (the added coupler generally bears an approximate molar ratio of from 1:1 to 1: 1;, with the yellow coupler); and it must be able to produce a shade which will compensate for the color imbalance at least partially. If not wholly then additional couplers of similar coupling potential characteristics should be applied. Since it is not necessary to use pure primary colors, the actual colors pro. duced will have anoverlap of spectral absorption but will produce in the combination just enough red, yellow and blue in all density areas to balance to a neutral black.

Classes of coupling components which have been found particularly suitable for balancing to a uniform neutral black in all density areas are as follows:

1. Compounds having the formula wherein R stands for a naphthalene nucleus unsubstituted ortho or para to the hydroxy group and X stands for a residue of the group consisting of -(iJ-NH2 ts and --'CNH-lC-NH2 I\|TH NH 2. Compounds of the formula wherein R2 stands fora member of the group'- consistmg of aryl, .alkyl, and. aralkyl groups; Rs

l. 7-hydroxynaphthalene-l-guanidine B-hydroxynaphthalene-l-biguanidine 7-hydroxynaphthalene-l-biguanidine 7-hydroxynaphthalene-Z-biguanidine 2,3-dihydroxynaphthalene 2,3-dihydroxynaphthalene-6-sulfonic acid 2,3-dihydroxynaphthalene-6-carboxylic acid 2-hydroxy-3 (,B-hydroxyethyl ether) -naphthalene 2-hydroxy-3Q3-N-dimethyl aminoethyl ether) '1' naphthalene 3. Cyclohexylacetoacetic acid amide Acetoacetic acid benzylamide Acetoacetic acid anilide Acetoacetic acid-o-methylanilide Acetoacetic acid-u-am nopyridine T hvdroxynaphthalene 1 acetoacetic acid amide Benzyl-acetic acid benzylamide When employing coupling components of the above classes for the purposes of this invention one should be selected from class 3, one from either class 2 or 1, and a third from class 2. Where two of the couplers are from class 2. one should be of slower coupling potential than the other and should produce compensating color tone.

Diazo compounds most suitable for my process are those derived from p-diamines of the benzene series, such as p-diazo-N- ethylhydroxyethyl aniline, 2-diazo-5-ethylamino-l-toluene, diazo of 1)- amino diphenyl amine, d azo of p-phenylene diamine, l-d azo-3-methyl-4-monoethvlamino benzene, and other similar p-diamines known to the art. invention will be more fully understood from the following detailed examples which are illustrative of the invention but are not intended in any way to limit the scope thereof. The parts are by weight unless otherwise specified.

Example 1 A coating solution was prepared by slowly mixing the following ingredients in the following proportions at room temperature:

Water cc 100 Glycerin ..cc 5 Citric ac d g 5 Zinc chloride g.. 5 Thiourea g 5 Acetoacetanilide -g 0.08 2.3-dihydroxynaphthalene g 0.1 2.3 dihydroxynaphthalene 6 sulfonic acid g 4 Zinc chloride double salt of p-diazo-N-dimethylaniline g 3 6 Example 2 TA coating solution was prepared by slowly mixing the following ingredients in the proportions given at room temperature:

Water -i an ion Glycerin cc 5 Citric acid e 5 Zinc chloride g 5 Thiourea g 5 Acetoacet-o-anisidide .g 0.5 2.3 dihydroxynaphthalene g 0.5 1 biguanidine-7-naphthol g 3 p-Diazo N ethylhydroxyethylan=line g 3 A stock paper was coated with the above solution in the usual manner employing a doctor blade to remove the excess solution and dried. Samples of this coated paper were then exposed to light under diapositives containing full density and half-tone areas and the thus exposed samples were developed in the usual manner by exposure to a m xture of water vapor and ammonia gas. Both the full density and half-tone areas of the diapositive and original were reproduced on the sensitized paper in a neutral black tone of uniform density.

Having now particularly set forth and described my invention, and having illustrated the best method of presenting it, what I now claim is:

1. Light sensitive diazotype layers capable of producing uniform neutral black images in all density areas comprising in combination a light sensitive diazo compound derived from a p-diamine of the benzene series two coupling components of varying coupling potential one of which is a compound of the formula wherein R2 stands for a member of the group consisting of aryl, alkyl, and aralkyl groups, R3 and R4 stand for a member of the group consisting of hydrogen, aryl, alkyl, aralkyl, acyl and 7 hydrogenated cyclic radicals, the other of which is selected from the group consisting of compounds having the formula NH-X wherein R stands for a naphthalene radical unsubstituted ortho or para to the hydroxy group and X for a residue of the group consisting of --("3-NHz and-C-NHC NHQ NH NH NH and compounds having the formula OH wherein R1 stands for a naphthalene radical bearing a sulfonic acid substituent and Y for a member of the group consisting of hydrogen, hydroxy alkyl, carboxy alkyl, and amino alkyl; and an additional coupling component of the same formula as (b) above but containing no nuclear sulfonic acid group when the second coupling component is a compound of the formula (b) said additional coupler being in a concentration bearing a ratio of from approximately 1:1 to 1: with respect to the first coupler.

arsenic 2- Light sensitive ldiazoiiitpe layers capable of producing a .black line of uniform neutral halftones comprising in combination alight sensitive d'iazo compound derived from a p-diamine of the benzene series and at least three coupling components, .one of which is .a compound of the formula wherein R stands for a naphthalene radical un substituted orth-o or para to the 'hydroxy group and X for a residue of the group consisting of and -o-NH o-N H l IH NH a second of which is .a compound of the formula OH 7R1(2)/ 3) wherein R1 stands for a napthalene radical and Y for a member of the group consisting of hydrogen, 'l'iyciroxy alkyl, carboxy alley and amono a1- kyl; and a third of which is a compound of the formula R3 I R-:- GOGH:-CO -.N

wherein R2 stands for a member of the group consisting of aryl .ailr yl, and :aral-kyl groups; R3 and R4 stand for a member of the group consisting of hydrogen, aryl, alkyl, aralkyl, acyl, and hydrogenated. cyclic radicals, the second coupler fleeing in a concentration ratio of from approximately 1:1 to 1: with respect to the third collpler.

'8 :A light sensitive d-iazotype layer capable at producing a black line of uniform neutral tones comprising in combination a diazo compound derived from a p-diamine of the benzene series and as coupling components Acetoacetanilide 2.3-dihydroxynaphthalene 2.3-dihydroxynaphthalene-G-sulfonic acid the second coupler being in a concentration ratio of approximately 11%; with respect to the first coupler.

4. A light sensitive diazctype layer capable of producing va black line of uniform neutral Ihalftones comprising a diazo compound derived from a p-diamine of the benzene series and as coupling components Acetoacet-o-anisidide 2.3-dihydroxynaphthalene 1-biguanidine- 7-naphth0l the second coupler being in a concentration ratio of vapproxima-tely 1:71 with respect to the first coupler.

SAM SHARES SLIFKIN.

RJEFERENGES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I'ENTS Number Name Date 1;807,7-61 'Sprongerts c June .2, 1931 1,816,989 Schmidt et a1. Aug. 4, 1931 "1,822,065 Sprongerts et a1. Sept. 8, 1931 1,989,065 Siclnn-idt e-t a1. Jan. 22,, 1935 2,037,542 Schmidt et al. .Apr. 14, 19.36 2,181,944 Kleine v Dec. 5., 1939 2,196,950 Zahn et al. c Apr. :9, 1940 FOREIGN PATENTS Number Country Date 7 660,087 France Feb, 12, 1929 331.4:59 Great Britain w July 3. 1930 

1. LIGHT SENSITIVE DIAZOTYPE LAYERS CAPABLE OF PRODUCING UNIFORM NEUTRAL BLACK IMAGES IN ALL DENSITY AREAS COMPRISING IN COMBINATION A LIGHT SENSITIVE DIAZO COMPOUND DERIVED FROM A P-DIAMINE OF THE BENZENE SERIES TWO COUPLING COMPONENTS OF VARYING COUPLING POTENTIAL ONE OF WHICH IS A COMPOUND OF THE FORMULA 